Skewed sheet correcting device and image forming apparatus

ABSTRACT

A skewed sheet correcting device includes: first and second shutter members which move to a first position in which the first and second shutter members are pushed to be movable by a leading edge of a sheet, a second position which is disposed further downstream of the sheet conveyance direction than the first position to latch the leading edge of the sheet, and a third position which allows the sheet to pass; and a movement regulating member which, when one of the shutter members does not move to the second position, regulates the other shutter member in the second position, and, when both the first and second shutter members move to the second position, allows the first and second shutter members to move to the third position.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a skewed sheet correcting device thatcorrects a skew of a sheet in an image forming apparatus and an imageforming apparatus including the same.

2. Description of the Related Art

Generally, a position where an image is recorded with respect to aposition of a sheet (hereinafter, referred to as “recording accuracy”)is an important element for an image quality in the image formingapparatus. Therefore, in an image forming apparatus of a related art,various skewed sheet correcting devices are provided in order to improvethe recording accuracy.

For example, a skewed sheet correcting device that allows a leading edgeof a sheet which is conveyed by a pair of conveying rollers to abut on ashutter member so as to be latched with the shutter member, rotates theshutter member to be retracted when the sheet forms a predeterminedloop, and allows the sheet to pass through the shutter member issuggested (U.S. Pat. No. 6,011,948).

However, in the skewed sheet correcting device of the related artdescribed above, generally the shutter member is urged by a urgingportion such as a spring in advance and a body of the sheet that forms apredetermined loop is affected by the urging force of the urging portionto push the shutter member so as to be retracted.

However, in order to allow a sheet having a lower rigidity such as athin sheet as compared with a sheet having a higher rigidity such as athick sheet to pass through the shutter member, it is required to setthe urging force of the shutter member to be low. In this case, thesheet having a higher rigidity such as a thick sheet undesirably passesthrough the shutter member without forming a sufficient loop and thusthe skew feeding of the sheet is not appropriately corrected.

In order to solve the above-mentioned problems, a configuration in whichthe shutter member is retracted under the condition where a detectorthat detects a leading edge of a sheet is provided and the skew feedingis appropriately corrected is suggested (Japanese Patent Laid-Open No.9-86726). However, when the detector that detects the leading edge ofthe sheet is provided, the number of components is increased, leading toa large size and a high cost of the device. Further, Japanese PatentLaid-Open No. 2008-120484 discloses a device including a first gate anda second gate where if the second gate is pushed by the leading edge ofa sheet to be conveyed so as to rotate to a correction position, arotation inhibition plate moves so as to allow the first gate to berotatable. However, this configuration may not correct the skew feedingof a sheet in which an angle at the second gate side between two anglesat the leading edge of the sheet is led.

SUMMARY OF THE INVENTION

It is desirable to provide a skewed sheet correcting device that iscapable of correcting the skew feeding regardless of the rigidity of asheet without increasing the size and the cost.

A skewed sheet correcting device according to the present inventionincludes: a conveying portion which conveys a sheet; first and secondshutter members which are arranged along a width direction perpendicularto the sheet conveyance direction and disposed downstream of theconveying portion in the sheet conveyance direction, wherein the firstand second shutter members move to a first position in which the shuttermembers are pushed to be movable by a leading edge of the sheet which isconveyed by the conveying portion, a second position which is disposedfurther downstream than the first position in the sheet conveyancedirection to latch the leading edge of the sheet, and a third positionwhich allows the sheet to pass; and a movement regulating portion which,when the first shutter member does not move to the second position,regulates the second shutter member that has moved in the secondposition in the second position, when the second shutter member does notmove to the second position, regulates the first shutter member whichhas moved in the second position in the second position, and, when boththe first shutter member and the second shutter member move to thesecond position, allows the first and second shutter members to move tothe third position.

According to the present invention, it is possible to surely correct theskew feeding of a sheet.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating an entire skewed sheetcorrecting device according to a first embodiment.

FIG. 2 is a cross-sectional diagram illustrating a state when a shuttermember of the skewed sheet correcting device according to the firstembodiment has a first position.

FIG. 3 is a cross-sectional diagram illustrating a state when theshutter member of the skewed sheet correcting device according to thefirst embodiment has a second position.

FIG. 4 is a cross-sectional diagram illustrating a state when theshutter member of the skewed sheet correcting device according to thefirst embodiment has a third position.

FIG. 5A is a plan view illustrating the state when the shutter member ofthe skewed sheet correcting device according to the first embodiment hasthe first position and FIG. 5B is a plan view illustrating a sheet statewhen the shutter member of the skewed sheet correcting device accordingto the first embodiment has the second position.

FIG. 6 is a plan view illustrating the state when the shutter member ofthe skewed sheet correcting device according to the first embodiment hasthe first position.

FIG. 7 is a plan view illustrating a state of a main part when theshutter member of the skewed sheet correcting device according to thefirst embodiment has the second position.

FIG. 8 is a perspective view illustrating a state of a main part whenthe shutter member of the skewed sheet correcting device according tothe first embodiment has the third position.

FIG. 9A is a perspective view illustrating a rotational position whenthe shutter member of the first embodiment has the first position or thesecond position and FIG. 9B is a perspective view illustrating arotational position when the shutter member of the first embodiment hasthe third position.

FIG. 10 is a plan view illustrating a state of a main part when theshutter member of the skewed sheet correcting device according to thefirst embodiment has the third position.

FIG. 11 is a perspective view illustrating a shape of a lever member ofthe skewed sheet correcting device according to the first embodiment.

FIG. 12A is a plan view illustrating a state of a main part when theshutter member of the skewed sheet correcting device according to thefirst embodiment start to rotate first and FIG. 12B is a plan viewillustrating a state of a main part when the shutter member of theskewed sheet correcting device according to the first embodiment startto rotate first.

FIG. 13A is a side view illustrating a state of a main part when theshutter member of the skewed sheet correcting device according to thefirst embodiment has the second position and FIG. 13B is a side viewillustrating a state of a main part when the shutter member of theskewed sheet correcting device according to the first embodiment has thethird position.

FIG. 14A is a side view illustrating a direction of the urging force bya torsion coil spring when the shutter member of the skewed sheetcorrecting device according to the first embodiment has the thirdposition and FIG. 14B is a side view illustrating a direction of theurging force by a torsion coil spring when the shutter member of theskewed sheet correcting device according to the first embodiment has thefirst position.

FIG. 15 is a cross-sectional view illustrating an entire configurationof a skewed sheet correcting device according to the present inventionand an image forming apparatus including the same.

FIG. 16 is a plan view illustrating a configuration of the skewed sheetcorrecting device according to the first embodiment.

FIG. 17 is a perspective view illustrating a configuration of the skewedsheet correcting device according to a second embodiment.

FIG. 18 is a plan view illustrating a state of a main part when ashutter member of the skewed sheet correcting device according to thesecond embodiment has a first position.

FIG. 19 is a cross-sectional view illustrating a state of a main partwhen the shutter member of the skewed sheet correcting device accordingto the second embodiment has the first position.

FIG. 20 is a perspective view illustrating a configuration of the mainpart of the skewed sheet correcting device according to the secondembodiment.

FIG. 21 is a plan view illustrating a state of the main part when theshutter member of the skewed sheet correcting device according to thesecond embodiment rotates first.

FIG. 22 is a plan view illustrating a state of a main part when theshutter member of the skewed sheet correcting device according to thesecond embodiment has a second position.

FIG. 23 is a perspective view illustrating a state of a main part whenthe shutter member of the skewed sheet correcting device according tothe second embodiment has a third position.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, with reference to accompanying drawings, exemplaryembodiments of the present invention will be illustratively described indetail. A size, a material, a shape, or a relative arrangement ofcomponents described in the following embodiments may be appropriatelyvaried depending on the configuration of an apparatus to which thepresent invention is applied or various conditions. Therefore, if notspecifically described, a scope of the present invention is not limitedthereto.

First Embodiment

First, an entire configuration of a skewed sheet correcting deviceaccording to a first embodiment and an image forming apparatus includingthe same will be described with reference to FIG. 15.

A sheet 4 which is accommodated in a feeding unit U and formed of apaper or a synthetic resin is supplied by a feeding roller 18 and thendivided by a dividing portion (not shown) one by one to be fed.

The sheet 4 which is fed by the feeding roller 18 is conveyed by a pairof conveying rollers 19 and then sent to a skewed sheet correctingdevice R disposed further downstream of a sheet conveyance direction(hereinafter, simply referred to as “downstream”). The skew feeding ofthe sheet 4 is corrected by the skewed sheet correcting device R andthen the sheet is conveyed to a photosensitive drum 23 as an imagebearing member (electrophotographic photosensitive member) that forms animage forming portion. Further, in the downstream in the vicinity of theskewed sheet correcting device R, and in the further upstream of thesheet conveyance direction compared to the photosensitive drum 23(hereinafter, simply referred to as “upstream”), a sensor 20 whichserves as a sheet detector is disposed to detect the passage of thesheet 4.

In the meantime, a surface of the photosensitive drum 23 is uniformlycharged by a charger. A laser scanner 24 controlled by the control unit25 scans laser light on the photosensitive drum 23 in accordance withimage information to form a latent image. A toner is supplied onto thephotosensitive drum 23 on which the latent image is formed from adevelopment device to form a toner image. A cleaning device that cleansthe photosensitive drum 23, a charger, the development device, and acleaning portion that cleans the photosensitive drum after beingtransferred which serve as a processer which operates therefor areprovided in a process cartridge 22 which serves as an image formingportion. The process cartridge 22 is detachably attachable to the imageforming apparatus.

At the time when the sensor 20 detects the sheet 4, the laser scanner 24forms a latent image on a surface of the photosensitive drum 23 to formthe toner image on the surface of the photosensitive drum 23 by a seriesof process operations of the process cartridge 22.

The sheet 4 is conveyed between the photosensitive drum 23 and thetransfer charger 21 in synchronization with the rotation of thephotosensitive drum 23 and the toner image which is formed on thephotosensitive drum 23 is transferred on the sheet 4 by the transfercharger 21.

Here, as illustrated in FIG. 1, the skewed sheet correcting device Rincludes a pair of registration rollers 8 and 10 and the rotational axisthereof is disposed so as to be parallel to the rotational axisdirection of the photosensitive drum 23. For example, as illustrated inFIG. 16, when the sheet 4 which is conveyed by the pair of conveyingrollers 19 and a pair of conveying rollers 16 is obliquely fed to thepair of registration rollers 8 and 10, the skew feeding is corrected bythe operation of the skewed sheet correcting device R. The sheet 4 onwhich skew feeding is corrected is conveyed so as to arrive on the imageforming portion to transfer the image thereon.

The sheet 4 on which the image is transferred is conveyed to a fixingunit 28 and heated and pressurized by the fixing unit 28 so that thetoner image is fixed on the sheet 4, and then discharged to the outsideof the device by a pair of discharging rollers 26 and 27.

Next, a mechanism of the skew feeding correction by the skewed sheetcorrecting device according to this embodiment will be described. FIG. 1is a perspective view illustrating an entire sheet conveying apparatusincluding a skewed sheet correcting device according to this embodimentand FIG. 2 is a cross-sectional diagram thereof.

In FIG. 1, the sheet 4 is conveyed by the pair of conveying rollers 16as a first conveying portion and approaches the vicinity of the pair ofregistration rollers 8 and 10 as a second conveying portion. One of thepair of registration rollers 8 and 10 is a driven registration roller 8which is provided at a driven registration roller shaft 7 and the otherone is a drive registration roller 10 which is provided at a driveregistration roller shaft 9. The pair of registration rollers 8 and 10is disposed further downstream of the sheet conveyance direction thanthe pair of conveying rollers 16.

In the vicinity of the pair of registration rollers 8 and 10, aplurality of shutter members 1 a and 1 b is provided in order to correctthe skew feeding of the sheet. The shutter members 1 a and 1 b areprovided in an axial direction (a width direction perpendicular to thesheet conveyance direction). The plurality of shutter members 1 a and 1b is disposed further downstream of the sheet conveyance direction thanthe pair of conveying rollers 16 and further upstream of the sheetconveyance direction than the pair of registration rollers 8 and 10. Theshutter members 1 a and 1 b are provided so as to be rotatableindependently from the driven registration roller shaft 7 of the drivenregistration roller 8 and are movable in a first position, a secondposition, and a third position. The first position is a position where aleading edge of the sheet 4 does not abut on the abutting surfaces 3 aand 3 b (FIG. 2), the second position is a position which is disposedfurther downstream of the sheet conveyance direction than the firstposition to latch the leading edge of the sheet 4 (FIG. 3), and thethird position is a position which allows passage of the sheet 4 (FIG.4).

In the upstream side of the sheet conveyance direction of nip portionsof the driven registration roller 8 and the drive registration roller10, the abutting surfaces 3 a and 3 b of the shutter members 1 a and 1 bare disposed (FIGS. 1 and 2) and the leading edge of the sheet 4 abutson the abutting surfaces 3 a and 3 b before entering the nip portion.The leading edge of the sheet 4 pushes the abutting surfaces 3 a and 3 bso that the shutter members 1 a and 1 b independently rotate around thedriven registration roller shaft 7.

The shutter members 1 a and 1 b may freely rotate between the firstposition in which the leading edge of the sheet 4 does not abut on theabutting surfaces 3 a and 3 b (FIG. 2) and the second position in whichthe leading edge of the sheet 4 is latched (FIG. 3). However, in orderto allow the shutter members 1 a and 1 b to rotate beyond the secondposition and move to the third position which allows the sheet 4 to pass(FIG. 4), both shutter members 1 a and 1 b which are all of the shuttermembers need to be in the second position.

For example, when the shutter member 1 b rotates prior to the shuttermember 1 a, the shutter member 1 b stops the rotation in the secondposition to wait until the shutter member 1 a reaches the secondposition. If the second position is set in a predetermined positionwhere the skew feeding of the sheet is appropriately corrected, anadvancing side of the skew feeding of the leading edge of the sheet 4needs to wait a lagging side by this operation so that the skew feedingof the sheet is corrected (FIGS. 5A and 5B). When both shutter members 1a and 1 b reach the second position, the shutter members 1 a and 1 b arerotatable beyond the second position. Thereafter, the leading edge ofthe sheet 4 enters the nip portions of the pair of registration rollers8 and 10 while pushing the shutter members 1 a and 1 b and the shuttermembers 1 a and 1 b to the third position by the leading edge of thesheet 4 which is conveyed to the pair of registration rollers 8 and 10(FIG. 4). If the sheet 4 completely passes the skewed sheet correctingdevice R, the shutter members 1 a and 1 b move from the third positionto the second position by the urging force which will be described belowand eventually return to the first position.

Next, as for the first embodiment that achieves a series of skew feedingcorrecting operations in which the shutter members 1 a and 1 b reachfrom the first position to the second position and the third position,pass the sheet, and then returns to the first position, the motions andthe roles of component parts will be described in detail.

The skewed sheet correcting device R is provided with a movementregulating portion configured as described below. The movementregulating portion abuts on a shutter member of the plurality of shuttermembers 1 a and 1 b which does not move to the second position toregulate the shutter member which moves to the second position in thesecond position. Further, all of the shutter members move to the secondposition to release the abutting state so that the movement regulatingportion allows all of the shutter members which move to the secondposition to move to the third position.

The movement regulating portion according to this embodiment includeslevers 2 a and 2 b as lever members (interlocking member) and a stoppermember 5 which will be described below.

As illustrated in FIGS. 2 and 6, in a rotational direction of theshutter members 1 a and 1 b, in an edge which is not an edge where theabutting surfaces 3 a and 3 b of the shutter members 1 a and 1 b aredisposed, the levers 2 a and 2 b are disposed. The levers 2 a and 2 bare rotatable around the same rotational support 6. Further, the levers2 a and 2 b are continuously applied with a force in a direction of anarrow A of FIG. 6 by the torsion coil springs 15 a and 15 b as an urgingpart. The urging force by the torsion coil springs 15 a and 15 b istransmitted to the shutter members 1 a and 1 b through the levers 2 aand 2 b and continuously urges the shutter members 1 a and 1 b in aposition of the first position. Here, the urging force of the torsioncoil springs 15 a and 15 b is set to be low enough to push the shuttermembers 1 a and 1 b to the second and third positions also in a sheethaving the lowest rigidity (for example, a thin paper having a basisweight of 52 g/m²) among the types of sheets which become a target ofthe image formation.

As illustrated in FIGS. 6 and 7, if the shutter members 1 a and 1 b arepushed by the leading edge of the sheet 4 so as to rotate, in connectionwith this, the levers 2 a and 2 b rotate around the rotational support6. The levers 2 a and 2 b abut the protrusions 11 a and 11 b provided onthe stopper member 5 as illustrated in FIGS. 7 and 8 in a position wherethe levers rotate by a predetermined amount from an initial positionillustrated in FIG. 6 so that the levers do not rotate around therotational support 6 anymore.

In the meantime, as illustrated in FIGS. 9A and 9B, a hook unit 13 isprovided at one end of the rotational support 6 and the rotationalsupport 6 is slidable along a groove of the guide 12. Further, if boththe shutter members 1 a and 1 b move to the second position, theabutting state of the levers 2 a and 2 b against the side of the stoppermember 5 is released and the levers 2 a and 2 b enter the groove 11 c ofthe stopper member 5 as illustrated in FIG. 10. However, since thelevers 2 a and 2 b are connected to each other through the commonrotational support 6, if one of the levers cannot enter the groove 11 cof the stopper member 5, the other lever cannot enter the groove 11 c ofthe stopper member 5. In other words, until both shutter members 1 a and1 b reach the second position, an end face 14 a of the lever 2 a or anend face 14 b of the lever 2 b illustrated in FIG. 11 abuts on the sideof the stopper member 5. Therefore, the levers 2 a and 2 b may not enterthe groove 11 c of the stopper member 5.

For example, as illustrated in FIG. 12B, when the shutter member 1 bmoves to the second position first, the lever 2 b abuts on the abuttingunit 11 b of the stopper member 5 so that the lever 2 b cannot rotatearound the rotational support 6 anymore. Thereafter, since the lever 2 bis continuously pushed by the shutter member 1 b, the lever 2 b mayenter the groove 11 c of the stopper member 5 while the rotationalsupport 6 is slid in a groove of a guide 12. However, when the shuttermember 1 a does not reach the second position, the end face 14 a of thelever 2 a abuts on the side of the stopper member 5. Therefore, thelever 2 a cannot enter the groove 11 c of the stopper member 5.Accordingly, the lever 2 b also cannot enter along the groove 11 c ofthe stopper member 5. Thus, when the shutter member 1 a does not reachthe second position, the shutter member 1 b cannot rotate beyond thesecond position.

In the meantime, as illustrated in FIG. 12A, similarly, in the casewhere the shutter member 1 a moves to the second position first, theshutter member 1 a cannot rotate beyond the second position when theshutter member 1 b does not reach the second position.

While the shutter member 1 b is in the second position and stops therotation, the sheet 4 is pushed in by the pair of conveying rollers 16which is the first conveying portion. Therefore, as illustrated in FIGS.5A and 5B, the leading edge of the sheet 4 pivots to push the abuttingsurface 3 a therein. Accordingly, the shutter member 1 a starts therotation and the lever 2 a which is pushed by the shutter member 1 aalso starts the rotation. As a result, at the time when the shuttermember 1 a moves to the second position and the lever 2 a abuts on theprotrusion 11 a as illustrated in FIG. 7, the abutting state of thelever 2 a against the side of the stopper member 5 is released so thatthe lever 2 a is capable of entering the groove of the stopper member 5.

Thus, since both the levers 2 a and 2 b are capable of entering thegroove of the stopper member 5, as illustrated in FIGS. 10 and 13A and13B, the shutter members 1 a and 1 b pushed at the leading edge of thesheet 4 rotate while allowing the levers 2 a and 2 b to enter the groovethe stopper member 5. The sheet is nipped by the pair of registrationrollers 8 and 10 while the shutter members 1 a and 1 b is moved by beingpushed by the sheet. If the shutter members 1 a and 1 b rotates at aconstant amount, the shutter members 1 a and 1 b are in the thirdposition and the leading edge of the sheet 4 passes the shutter members1 a and 1 b as illustrated in FIG. 4.

When a trailing edge of the sheet completely passes the shutter members1 a and 1 b, the levers 2 a and 2 b are extruded from the groove of thestopper member 5 by the urging force of the torsion coil springs 15 aand 15 b (force in a direction of an arrow B illustrated in FIG. 14A)(FIGS. 14A and 14B). In other words, the urging force of the torsioncoil springs 15 a and 15 b is applied in a direction that rotates thelevers 2 a and 2 b around the rotational support 6 (in a direction of anarrow A illustrated in FIGS. 6 and 14B) and the levers 2 a and 2 breturns to the state of FIG. 6. In connection with a series of motionsof the levers 2 a and 2 b, the shutter members 1 a and 1 b return fromthe third position to the second and first positions.

As described above, according to this embodiment, under a conditionwhere the plurality of shutter members 1 a and 1 b are pushed to thesecond position that latches the leading edge of the sheet, all of theplurality of shutter members 1 a and 1 b is retracted from the secondposition to the third position that allows the sheet to pass. Therefore,it is possible to surely correct the skew feeding of a sheet regardlessof the rigidity of the sheet without increasing the size and the cost ofthe device.

Second Embodiment

Next, as for a second embodiment that achieves a series of skew feedingcorrecting operations, motions and roles of component parts will bedescribed in detail.

Also in the second embodiment, similarly to the above-describedembodiment, the skewed sheet correcting device R has a movementregulating portion that is configured as described below. The movementregulating portion according to this embodiment includes a cylindermember 38 as a rotational member which will be described below, slidepins 37 a and 37 b as a sliding member (interlocking member), and astopper member 31.

As illustrated in FIG. 17, the shutter members 1 a and 1 b are urged tothe first position by the urging force of the torsion coil springs 39 aand 39 b as a urging portion. Further, in an edge which is not an edgewhere sheet abutting surfaces of the shutter members 1 a and 1 b aredisposed, skewed planes 35 a and 35 b are disposed as illustrated inFIG. 18. In a position that contacts with the skewed planes 35 a and 35b, the slide pins 37 a and 37 b are disposed. That is, slide pins 37 aand 37 b are provided so as to correspond to the shutter members 1 a and1 b, respectively.

In the meantime, as illustrated in FIG. 17, at an inside of the shuttermembers 1 a and 1 b, the cylinder member 38 is provided so as to berotatable around the driven registration roller shaft 7. The cylindermember 38 is applied with a force in a direction of an arrow of FIG. 19by an urging portion (eccentricity of a center of the cylinder member, atorsion coil spring, or a compression spring) which is not illustrated.Further, a groove 33 is provided in the cylinder member 38 in an axialdirection as illustrated in FIG. 20.

As illustrated in FIG. 20, the above-mentioned slide pins 37 a and 37 bare disposed in the groove 33 of the cylinder member 38. The slide pins37 a and 37 b abut on the shutter members 1 a and 1 b, respectively, soas to be slidable in an axial direction along the groove 33 of thecylinder member 38 in accordance with the movement of the shuttermembers 1 a and 1 b. Further, the slide pins 37 a and 37 b rotate aroundthe driven registration roller shaft 7 together with the cylinder member38. Further, a compression spring 30 is provided in the groove 33 so asto outwardly apply a force to the slide pins 37 a and 37 b.

Further, as illustrated in FIG. 17, the stopper member 31 is disposedoutside the shutter members 1 a and 1 b so as to be fixed. Asillustrated in FIG. 20, the stopper member 31 has edges 31 a and 31 band the slide pins 37 a and 37 b abut on the edges 31 a and 31 b,respectively. The stopper member 31 abuts on a slide pin whichcorresponds to a shutter member that does not move to the secondposition so as to regulate the shutter member which moves to the secondposition from moving to the third position.

Hereinafter, operations of members that correct a sheet fed to be skewedwill be described. Here, operations of members when the shutter member 1b is pushed in the sheet prior to the shutter member 1 a will bedescribed.

If the shutter member 1 b is pushed in the sheet to start the rotation,as illustrated in FIG. 21, the slide pin 37 b is pushed in a skewedplane 35 b of the shutter member 1 b. However, since the slide pin 37 babuts on the edge 31 b of the stopper member 31, the slide pin cannotrotate for every cylinder member 38. However, the slide pin 37 b isslidable in the axial direction so that as illustrated in FIG. 21, theslide pin 37 b slides in the axial direction along the groove 33 inconnection with the rotation of the shutter member 1 b.

If the shutter member 1 b is pushed in the sheet to rotate to the secondposition, the slide pin 37 b is deviated from the edge 31 b of thestopper member 31. In this case, the shutter member 1 b pushes theabutting surface 38 b of the cylinder member 38 to rotate the cylindermember 38. However, if the shutter member 1 a does not reach the secondposition, the slide pin 37 a abuts on the edge 31 a of the stoppermember 31. Accordingly, the cylinder member 38 does not rotate. As aresult, as illustrated in FIG. 21, the shutter member 1 b cannot rotateover the second position.

Even while the shutter member 1 b stops in the second position, thesheet 4 is pushed in by the pair of conveying rollers 16 which is thefirst conveying portion. Therefore, as illustrated in FIGS. 5A and 5B,the leading edge of the sheet 4 pivots to push the abutting surface 3 aof the shutter member 1 a. By doing this, the shutter member 1 a startsto rotate and the slide pin 37 a which is pushed in the skewed plane 35a of the shutter member 1 a starts to slide along the groove 33 in theaxial direction.

As a result, at a time when the shutter member 1 a moves to the secondposition and the slide pin 37 a is deviated from the edge 31 a of theshutter member 1 a as illustrated in FIG. 22, the cylinder member 38 isrotatable. Accordingly, the shutter members 1 a and 1 b are alsorotatable beyond the second position. As illustrated in FIG. 23, theshutter members 1 a and 1 b which are pushed in the leading edge of thesheet 4 pushes the abutting surfaces 38 a and 38 b of the cylindermember 38 and rotates together with the cylinder member 38. If theshutter members 1 a and 1 b rotate at a constant rotation amount, theshutter members 1 a and 1 b are in the third position and the leadingedge of the sheet 4 passes the shutter members 1 a and 1 b asillustrated in FIG. 4.

If the trailing edge of the sheet 4 completely passes the shuttermembers 1 a and 1 b, the shutter members 1 a and 1 b return from thethird position to the second and first positions by the urging force ofthe torsion coil springs 39 a and 39 b. Further, the cylinder member 38in which the pushing by the shutter members 1 a and 1 b is releasedreturns to the initial position by a urging portion which is notillustrated. If the cylinder member 38 returns to an initial position,the slide pins 37 a and 37 b return to the outside by the urging forceof the compression spring 30.

As described above, this embodiment may achieve the same effect as theabove-described embodiment. That is, under a condition where theplurality of shutter members 1 a and 1 b is pushed to the secondposition that latches the leading edge of the sheet, all of theplurality of shutter members 1 a and 1 b is retracted from the secondposition to the third position that allows the sheet to pass. Therefore,it is possible to surely correct the skew feeding of a sheet regardlessof the rigidity of the sheet without increasing the size and the cost ofthe device.

Other Embodiments

In the above-described embodiment, as the process cartridge which isdetachably attachable to the image forming apparatus, the processcartridge having the photosensitive drum, and a charger, a developmentportion, and a cleaning portion which serve as a processor whichoperates for the photosensitive drum integrally combined therein isdescribed. However, the process cartridge is not limited thereto. Theprocessor cartridge may have any one of the charger, a developmentportion, and the cleaning portion other than the photosensitive drum tobe integrally combined.

In the above-described embodiment, a configuration where the processcartridge including the photosensitive drum is detachably attachable tothe image forming apparatus is described, but the invention is notlimited thereto. For example, an image forming apparatus may haveconfiguration members which are assembled therein or have detachableconfiguration members.

In the above-described embodiment, even though a printer is exemplifiedas an image forming apparatus, the invention is not limited thereto. Forexample, the image forming apparatus may be other image formingapparatus such as a copying machine or a facsimile or other imageforming apparatus such as a multifunctional peripheral in whichfunctions of the copying machine and the facsimile are combined. If thepresent invention is applied to the skewed sheet correcting device usedin the image forming apparatus, the same effect may be obtained.

Further, in the above-described embodiment, even though a configurationin which the skewed sheet correcting device that corrects the skewfeeding of the sheet is applied to the conveying apparatus that conveysthe sheet in the image forming portion that forms an image on the sheetsuch as a recording sheet as a recording target is exemplified, theinvention is not limited thereto. For example, if the skewed sheetcorrecting device that corrects the skew feeding of the sheet is appliedto the conveying apparatus that conveys the sheet to an image readingunit that reads an image on the sheet such as an original as a readingtarget, the same effect may be obtained.

In the above-described embodiment, even though an electrophotographicsystem is exemplified as a recording system, the invention is notlimited thereto. For example, other recording system such as an inkjetsystem may be applied thereto.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications, equivalent structures and functions.

This application claims the benefit of Japanese Patent Application No.2012-015307, filed Jan. 27, 2012, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. A skewed sheet correcting device, comprising: aconveying portion which conveys a sheet; first and second shuttermembers which are arranged along a width direction perpendicular to thesheet conveyance direction and disposed downstream of the conveyingportion in the sheet conveyance direction, wherein the first and secondshutter members move to a first position in which the shutter membersare pushed to be movable by a leading edge of the sheet which isconveyed by the conveying portion, a second position which is disposedfurther downstream than the first position in the sheet conveyancedirection to latch the leading edge of the sheet, and a third positionwhich allows the sheet to pass; and a movement regulating portion which,when the first shutter member does not move to the second position,regulates the second shutter member that has moved in the secondposition in the second position, when the second shutter member does notmove to the second position, regulates the first shutter member whichhas moved in the second position in the second position, and, when boththe first shutter member and the second shutter member move to thesecond position, allows the first and second shutter members to move tothe third position.
 2. The skewed sheet correcting device according toclaim 1, wherein the movement regulating portion includes: a first levermember which rotates in connection with the first shutter member; asecond lever member which rotates around a common rotational shaft tothe first lever member in connection with the second shutter member; anda stopper member which, when the first shutter member does not move tothe second position, regulates the movement of the second shutter memberthat has moved in the second position to the third position by abuttingon the first lever member, and, when the second shutter member does notmove to the second position, regulates the movement of the first shuttermember that has moved in the second position to the third position byabutting on the second lever member, and both the first shutter memberand the second shutter member rotate to the second position to releasean abutting state of the first and second lever members on the stoppermember so that the first and second shutter members move to the thirdposition.
 3. The skewed sheet correcting device according to claim 1,wherein the movement regulating portion includes: a rotating memberwhich is pushed by the first and second shutter members to rotatetogether with the first and second shutter members; a first slide memberwhich is disposed in the rotating member so as to correspond to thefirst shutter member and moves in an axial direction with respect to therotating member in accordance with the movement of the first shuttermember; a second slide member which is disposed in the rotating memberso as to correspond to the second shutter member and moves in an axialdirection with respect to the rotating member in accordance with themovement of the second shutter member; and a stopper member which, whenthe first shutter member does not move to the second position, regulatesthe movement of the second shutter member that has moved in the secondposition to the third position by abutting on the first slide member,and, when the second shutter member does not move to the first position,regulates the movement of the first shutter member that has moved thefirst position to the third position by abutting on the second slidemember, and the first slide member and the second slide member move asboth the first shutter member and the second shutter member move to thesecond position to release an abutting state of the first and secondslide members on the stopper member so that the first and second shuttermembers move to the third position.
 4. The skewed sheet correctingdevice according to claim 1, further comprising a pair of rollers whichis disposed downstream of the conveying portion in the sheet conveyancedirection, wherein the sheet is nipped by the pair of rollers while thefirst and second shutter is moved by being pushed by the sheet.
 5. Theskewed sheet correcting device according to claim 1, further comprisinga urging portion which applies a force to the first and second shuttermembers at the first position.
 6. An image forming apparatus,comprising: an image forming portion which forms an image on a sheet;and a sheet conveying apparatus which conveys the sheet to the imageforming portion, wherein the sheet conveying apparatus includes: aconveying portion which conveys the sheet; first and second shuttermembers which are arranged along a width direction perpendicular to asheet conveyance direction and disposed downstream of the conveyingportion in the sheet conveyance direction, wherein the first and secondshutter members move to a first position in which the first and secondshutter members are pushed to be movable by a leading edge of the sheetwhich is conveyed by the conveying portion, a second position which isdisposed further downstream than the first position in the sheetconveyance direction to latch the leading edge of the sheet, and a thirdposition which allows the sheet to pass; and a movement regulatingportion which, when the first shutter member does not move to the secondposition, regulates the second shutter member that has moved in thesecond position in the second position, when the second shutter memberdoes not move to the second position, regulates the first shutter memberthat has moved in the second position in the second position, and, whenboth the first shutter member and the second shutter member move to thesecond position, allows the first and second shutter members to move inthe third position.
 7. The image forming apparatus according to claim 6,wherein the movement regulating portion includes: a first lever memberwhich rotates in connection with the first shutter member; a secondlever member which rotates around a common rotational shaft to the firstlever member in connection with the second shutter member; and a stoppermember which, when the first shutter member does not move to the secondposition, regulates the movement of the second shutter member that hasmoved in the second position to the third position by abutting on thefirst lever member, and, when the second shutter member does not move tothe second position, regulates the movement of the first shutter memberthat has moved in the second position to the third position by abuttingon the second lever member, and both the first shutter member and thesecond shutter member rotate to the second position to release anabutting state of the first and second lever members on the stoppermember so that the first and second shutter member move to the thirdposition.
 8. The image forming apparatus according to claim 6, whereinthe movement regulating portion includes: a rotating member which ispushed by the first and second shutter members to rotate together withthe first and second shutter members; a first slide member which isdisposed in the rotating member so as to correspond to the first shuttermember and moves in an axial direction with respect to the rotatingmember in accordance with the movement of the first shutter member; asecond slide member which is disposed in the rotating member so as tocorrespond to the second shutter member and moves in an axial directionwith respect to the rotating member in accordance with the movement ofthe second shutter member; and a stopper member which, when the firstshutter member does not move to the second position, regulates themovement of the second shutter member that has moved in the secondposition to the third position by abutting on the first slide member,and, when the second shutter member does not move to the first position,regulates the movement of the first shutter member that has moved to thefirst position to the third position by abutting on the second slidemember, and the first slide member and the second slide member move asboth the first shutter member and the second shutter member move to thesecond position to release the abutting state of the first and secondslide members against the stopper member so that the first and secondshutter member move to the third position.
 9. The image formingapparatus according to claim 6, further comprising a pair of rollerswhich is disposed downstream of the conveying portion in the sheetconveyance direction, wherein the sheet is nipped by the pair of rollerswhile the first and second shutter is moved by being pushed by thesheet.
 10. The image forming apparatus according to claim 6, furthercomprising a urging portion which applies a force to the first andsecond shutter members at the first position.
 11. A skewed sheetcorrecting device, comprising: a conveying portion which conveys asheet; first and second shutter members which are arranged along a widthdirection perpendicular to the sheet conveyance direction and disposeddownstream of the conveying portion in the sheet conveyance direction,wherein the first and second shutter members move to a first position inwhich the shutter members are pushed to be movable by a leading edge ofthe sheet which is conveyed by the first conveying portion, a secondposition which is disposed further downstream than the first position inthe sheet conveyance direction to latch the leading edge of the sheet,and a third position which allows the sheet to pass; a firstinterlocking member which interlocks with the first shutter member; asecond interlocking member which interlocks with the second shuttermember; a stopper member which, when the first shutter member does notmove to the second position, regulates the movement of the secondshutter member that has moved to the second position to the thirdposition by abutting on the first interlocking member, and, when thesecond shutter member does not move to the second position, regulatesthe movement of the first shutter member that has moved to the secondposition to the third position by abutting on the second interlockingmember, and the abutting state of the first and second interlockingmembers against the stopper member is released if both the first shuttermember and the second shutter member rotate to the second position,thereby the first and second shutter member can move to the thirdposition.
 12. The skewed sheet correcting device according to claim 11,further comprising a pair of rollers which is disposed downstream of theconveying portion in the sheet conveyance direction, wherein the sheetis nipped by the pair of rollers while the first and second shutter ismoved by being pushed by the sheet.